The present invention relates generally to the art of cathode sputtering of indium oxide films, and more particularly to the art of magnetic sputtering of multiple layer films such as indium oxide and silver.
U.S. Pat. No. 4,094,763 to Gillery et al discloses producing transparent, electroconductive articles by cathode sputtering metals such as tin and indium onto refractory substrates such as glass at a temperature above 400.degree. F. in a low pressure atmosphere containing a controlled amount of oxygen.
U.S. Pat. No. 4,113,599 to Gillery teaches a cathode sputtering technique for the reactive deposition of indium oxide in which the flow rate of oxygen is adjusted to maintain a constant discharge current while the flow rate of argon is adjusted to maintain a constant pressure in the sputtering chamber.
U.S. Pat. No. 4,166,018 to Chapin describes a sputtering apparatus in which a magnetic field is formed adjacent a planar sputtering surface, the field comprising arching lines of flux over a closed loop erosion region on the sputtering surface.
U.S. Pat. No. 4,201,649 to Gillery discloses a method for making low resistance indium oxide thin films by first depositing a very thin primer layer of indium oxide at low temperature before heating the substrate to deposit the major thickness of the conductive layer of indium oxide by cathode sputtering at typically high cathode sputtering temperatures.
High light transmittance, low emissivity coatings of the type metal oxide/metal/metal oxide are known in the cathode sputtering art. Indium oxide/silver/indium oxide has good optical and spectral properties. However, in the cathode sputtering of multiple layer films such as indium oxide/silver/indium oxide, adhesion between the coating layers is a characteristic in need of improvement. For example, the adhesion of indium oxide to silver is so poor that if a coated glass sheet is to be assembled into a double glazed unit, the coating must be stripped from the area of the unit seals to avoid seal failure. In addition, when the top oxide layer is deposited, oxidation of the intermediate metallic layer reduces its conductivity and emissivity and is therefore undesirable. The present invention deals with both of these problems.